Last winter, a weak La Niña bloomed across the Pacific. It sent flume after flume of rain to North America and irrigated half the continent. Water penetrated deep into the soil of Western forests, and mammoth snowdrifts stacked up across the Sierra Nevadas. California’s drought ended in the washout.

“This will become an important year for [anecdotes about] the importance of temperature. Despite the fact that these forests were really soaked down this winter and spring, these heat waves have dried things out enough to promote really large fires,” says Park Williams, a research scientist at the Lamont-Doherty Earth Observatory at Columbia University.

“This heat wave is having a way worse influence on fire than it would in absence of human-caused warming.”

In other words, the weeks of heat that baked the West in July and August were enough to wipe away some of the fire-dampening effect of the winter storms.

“The last 60 to 90 days have been exceptionally warm and dry, the perfect recipe for drying out fuels (the one ingredient besides ignitions you need for fire in these systems),” said John Abatzoglou, a professor of geography at the University of Idaho, in an email. “I was running a few numbers this morning, and the last 60 days have been record warm from Spokane, Washington, to Medford, Oregon; both Seattle and Missoula earlier this summer set records for the longest number of days without measurable rain.”

This excessive heat can have an outsize effect on the size of forest fires. For more than three decades, wildfire researchers have known that fire and aridity, which is controlled by heat, exist in an exponential relationship. Every degree of warming does more to promote fire than the previous degree of warming, Williams said.

“Now, thinking about temperature trends due to human-caused climate change, we think that the western United States is 1.5 [degrees] Celsius, or 3 degrees Fahrenheit, hotter than it would be in absence of climate change. And there’s a heat wave on top of that,” said Williams. “Because of the exponential influence of temperature, that means that this heat wave is having a way worse influence on fire than it would in absence of human-caused warming.”

In the runaway consequences of each additional degree of warming, wildfires are a “canary in the coal mine” for the effects of climate change, Williams said.

“The added forest fire area—due to just the degree and a half Celsius of warming—equaled the area of Massachusetts and Connecticut combined,” Williams told me.

The area of annual burned forest in the Pacific Northwest has increased by nearly 5000 percent.

Other researchers have arrived at similar conclusions. A paper published in Science last year found that “large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons.” The mid-1980s is also when most scientists argue that the effects of global warming began to be broadly felt.

Fires have not only been increasing in size due to climate change. In the early 20th century, state and federal governments began aggressively fighting wildfires and trying to keep them as small as possible. This has caused denser and more fire-prone forests than the long-term average for the West, which has led to more massive and uncontrollable fires.

People have also lengthened the season by starting fires—through errant fireworks, unattended campfires, or arson—earlier in the spring and later in the fall. In a human-free environment, fires could only start after a lightning strike, which only follow from summertime thunderstorms.

“Since the 1980s, we’ve only burnt about 10 percent of the western U.S. forests. And that number to me means that there’s still a whole lot more to burn,” Williams said. He estimated that it would take another several decades for that excess century of fuel to burn out of the American woods. And in the meantime, the planet will only get hotter.

“According to climate models, by the end of this century, the western United States is still projected to warm by about another 3.5 degrees Celsius,” he told me. “And when we remember that the relationship between temperature and fire is exponential ... we’re really talking about a very different western United States in 50 years.”

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Five days after Hurricane Maria made landfall in Puerto Rico, its devastating impact is becoming clearer.

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A small group of programmers wants to change how we code—before catastrophe strikes.

There were six hours during the night of April 10, 2014, when the entire population of Washington State had no 911 service. People who called for help got a busy signal. One Seattle woman dialed 911 at least 37 times while a stranger was trying to break into her house. When he finally crawled into her living room through a window, she picked up a kitchen knife. The man fled.

The 911 outage, at the time the largest ever reported, was traced to software running on a server in Englewood, Colorado. Operated by a systems provider named Intrado, the server kept a running counter of how many calls it had routed to 911 dispatchers around the country. Intrado programmers had set a threshold for how high the counter could go. They picked a number in the millions.

The greatest threats to free speech in America come from the state, not from activists on college campuses.

The American left is waging war on free speech. That’s the consensus from center-left to far right; even Nazis and white supremacists seek to wave the First Amendment like a bloody shirt. But the greatest contemporary threat to free speech comes not from antifa radicals or campus leftists, but from a president prepared to use the power and authority of government to chill or suppress controversial speech, and the political movement that put him in office, and now applauds and extends his efforts.

The most frequently cited examples of the left-wing war on free speech are the protests against right-wing speakers that occur on elite college campuses, some of which have turned violent.New York’s Jonathan Chait has described the protests as a “war on the liberal mind” and the “manifestation of a serious ideological challenge to liberalism—less serious than the threat from the right, but equally necessary to defeat.” Most right-wing critiques fail to make such ideological distinctions, and are far more apocalyptic—some have unironically proposed state laws that define how universities are and are not allowed to govern themselves in the name of defending free speech.

A growing body of research debunks the idea that school quality is the main determinant of economic mobility.

One of the most commonly taught stories American schoolchildren learn is that of Ragged Dick, Horatio Alger’s 19th-century tale of a poor, ambitious teenaged boy in New York City who works hard and eventually secures himself a respectable, middle-class life. This “rags to riches” tale embodies one of America’s most sacred narratives: that no matter who you are, what your parents do, or where you grow up, with enough education and hard work, you too can rise the economic ladder.

A body of research has since emerged to challenge this national story, casting the United States not as a meritocracy but as a country where castes are reinforced by factors like the race of one’s childhood neighbors and how unequally income is distributed throughout society. One such study was published in 2014, by a team of economists led by Stanford’s Raj Chetty. After analyzing federal income tax records for millions of Americans, and studying, for the first time, the direct relationship between a child’s earnings and that of their parents, they determined that the chances of a child growing up at the bottom of the national income distribution to ever one day reach the top actually varies greatly by geography. For example, they found that a poor child raised in San Jose, or Salt Lake City, has a much greater chance of reaching the top than a poor child raised in Baltimore, or Charlotte. They couldn’t say exactly why, but they concluded that five correlated factors—segregation, family structure, income inequality, local school quality, and social capital—were likely to make a difference. Their conclusion: America is land of opportunity for some. For others, much less so.

One hundred years ago, a retail giant that shipped millions of products by mail moved swiftly into the brick-and-mortar business, changing it forever. Is that happening again?

Amazon comes to conquer brick-and-mortar retail, not to bury it. In the last two years, the company has opened 11 physical bookstores. This summer, it bought Whole Foods and its 400 grocery locations. And last week, the company announced a partnership with Kohl’s to allow returns at the physical retailer’s stores.

Why is Amazon looking more and more like an old-fashioned retailer? The company’s do-it-all corporate strategy adheres to a familiar playbook—that of Sears, Roebuck & Company. Sears might seem like a zombie today, but it’s easy to forget how transformative the company was exactly 100 years ago, when it, too, was capitalizing on a mail-to-consumer business to establish a physical retail presence.

The foundation of Donald Trump’s presidency is the negation of Barack Obama’s legacy.

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National Geographic Magazine has opened its annual photo contest, with the deadline for submissions coming up on November 17.

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What the Trump administration has been threatening is not a “preemptive strike.”

Donald Trump lies so frequently and so brazenly that it’s easy to forget that there are political untruths he did not invent. Sometimes, he builds on falsehoods that predated his election, and that enjoy currency among the very institutions that generally restrain his power.

That’s the case in the debate over North Korea. On Monday, The New York Timesdeclared that “the United States has repeatedly suggested in recent months” that it “could threaten pre-emptive military action” against North Korea. On Sunday, The Washington Post—after asking Americans whether they would “support or oppose the U.S. bombing North Korean military targets” in order “to get North Korea to give up its nuclear weapons”—announced that “Two-thirds of Americans oppose launching a preemptive military strike.” Citing the Post’s findings, The New York Times the same day reported that Americans are “deeply opposed to the kind of pre-emptive military strike” that Trump “has seemed eager to threaten.”

More comfortable online than out partying, post-Millennials are safer, physically, than adolescents have ever been. But they’re on the brink of a mental-health crisis.

One day last summer, around noon, I called Athena, a 13-year-old who lives in Houston, Texas. She answered her phone—she’s had an iPhone since she was 11—sounding as if she’d just woken up. We chatted about her favorite songs and TV shows, and I asked her what she likes to do with her friends. “We go to the mall,” she said. “Do your parents drop you off?,” I asked, recalling my own middle-school days, in the 1980s, when I’d enjoy a few parent-free hours shopping with my friends. “No—I go with my family,” she replied. “We’ll go with my mom and brothers and walk a little behind them. I just have to tell my mom where we’re going. I have to check in every hour or every 30 minutes.”

Those mall trips are infrequent—about once a month. More often, Athena and her friends spend time together on their phones, unchaperoned. Unlike the teens of my generation, who might have spent an evening tying up the family landline with gossip, they talk on Snapchat, the smartphone app that allows users to send pictures and videos that quickly disappear. They make sure to keep up their Snapstreaks, which show how many days in a row they have Snapchatted with each other. Sometimes they save screenshots of particularly ridiculous pictures of friends. “It’s good blackmail,” Athena said. (Because she’s a minor, I’m not using her real name.) She told me she’d spent most of the summer hanging out alone in her room with her phone. That’s just the way her generation is, she said. “We didn’t have a choice to know any life without iPads or iPhones. I think we like our phones more than we like actual people.”

Senators Lindsey Graham and Bill Cassidy sparred with Bernie Sanders and Amy Klobuchar on CNN hours after their bill dismantling Obamacare appeared to collapse.

Ordinarily, you debate to stave off defeat. But for Senators Lindsey Graham and Bill Cassidy on Monday night, the defeat came first.

By the time the two GOP senators stepped on CNN’s stage Monday night for a prime-time debate over their health-care proposal, they knew they had already lost.

A few hours earlier, Senator Susan Collins became the third Republican to formally reject the pair’s legislation to repeal and replace the Affordable Care Act, effectively killing its chances for passage through the Senate this week. Graham and Cassidy had hoped to use the forum to make a closing argument for their plan, and to line it up against Senator Bernie Sanders and his call for a single-payer, “Medicare-for-All” health-care system. Instead, the two senators found themselves defending a proposal that was no less hypothetical—and probably much less popular—than Sanders’s supposed liberal fantasy.